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9o                           POTASSIUM PERMANGANATE

solution (i : 20) free from iodates : in presence of nitrites, a blue coloration
is obtained almost immediately.1

7. Quantitative Determination.—Analogous to that of sodium nitrate
(see Fertilisers).

Nitre for the manufacture of gunpowder should not, according to French
requirements, contain more than 0-033% of sodium chloride ; according to the
German, not more than 0-010%, and according to the English and Italian, not
more than 0-005%. Further, it should contain only traces of chlorates and


Various potassium oxalates exist: Neutral oxahite, Is./*/),, -|~ H2Q —:
184-2, colourless crystals, soluble in 3 parts of cold water to a neutral solu-
tion. The A cid oxalate or bioxalate, KHCa04 + H»() =--• ^.(j-i, in colourless,
transparent, rhomboidal crystals, soluble in 25 parts of cold water to an
acid solution. The Quadroxakite or Telroxdate, KH('aO«> Hs-CgOo, + 2H20
= 254-1, colourless crystals soluble in about 55 parts ul' cold water to tin
acid solution. Salts of Sorrel, a mixture of the In- and tetr-oxalate, soluble
in 40 parts of water giving an acid solution. In these products the impurities
to be tested for are chlorides, sulphates and lead :

1.  Chlorides,  Sulphates.- -The solution, acidified  with   nitric acid,
is tested with silver nitrate or barium chloride.

2.  Lead and other Heavy Metals,......i, dissolved in water and

rendered alkaline with ammonia, is treated with ammonium sulphide,

3.  Determination of the Oxalic Acid............The tolul acid is determined,

either by precipitating as calcium oxalate with ammonia and calcium chloride,
and weighing as lime (i part ("aO -   1-607 part: Ha(VM» or volumetrically
with permanganate (i c.c. ,N/io-perma,nganate •    0-0045 gram Hara()4).

The free acid, derived from the bioxalate or telroxalate and used to
deduce the nature of the acid salt, is determined by titration with N-alkali
in presence of phenolphthalein : i c.c. N-alkali 0*045 gram na('a()4.

i gram KHCa()4 + Ha() requires (1-85 c.c. N-alkali.

I gram KHC204, HaCaO4 + 2.1I8(.) requires ii-8t> c.c.  N -alkali.


KMn04 :..-.• 158

Violet-reel crystals of metallic lustre, soluble' in 16 pints of cold water.
The tests made; are as follows :

1.  Chlorides, Sulphates......2 grains are dissolved in 50 c.c. of water

and the solution heated with it) c.c. of alcohol until deeolorisation is com-
plete.    The liquid is filtered and the filtrate acidified with nitric acid and
tested with silver nitrate and with barium chloride,

2.  Nitrates.—i grain is dissolved in 10 c.c. of water and the solution,
after deeolorisation with oxalic acid, mixed with fin equal volume of cone,

1 If the potassium iodide is not absolutely free from iodates, tin; blue coloration
may also appear, at any rate after some time. The test is, of, invalid if tho
nitre contains iodates. the i : 10 solution of the nitre are added 6 drops of